Morphometric analysis of the insertion of the upper head of the lateral pterygoid muscle

Abstract

Objective. This article reports on the morphometric characteristics of the upper head of the lateral pterygoid muscle. Study design. Several morphologic characteristics were initially examined in 40 postmortem specimens. The length of the upper head of the lateral pterygoid muscle was determined in 34 specimens. Of the 26 specimens in which the upper head of the lateral pterygoid muscle was found to be inserted into the meniscus and condyle, 22 specimens were examined microscopically to morphometrically quantify the proportion of muscle fibers to their respective insertions. Results. The upper head of the lateral pterygoid muscle was approximately 33.3 mm in length and was significantly longer in males. There were no age-related differences. Approximately 29.5% of the fibers of this muscle were inserted into the meniscus of the temporomandibular joint. Conclusion. This study demonstrated that the insertion of the upper head of the lateral pterygoid muscle to the meniscus ranged from a fleshy mass to a few fibers. The number of fibers entering both the meniscus and the condyle decreased correspondingly as they approached the joint and could be interpreted as this muscle having a tendon of insertion into the meniscus.